This invention relates to a power seat for vehicle which is moved forward and backward by a motor.
Generally, a power seat for vehicle includes an upper channel and a lower channel fixedly attached on a floor of a vehicle. A seat is mounted on the upper channel. The upper channel is engaged with the lower channel, and movable along the longitudinal direction of the lower channel. The power seat is provided with a nut unit. The nut unit is secured to the lower channel. A driver shaft is passed through the nut unit, and is rotated in forward and backward directions by an electric motor to slide the upper channel.
The nut unit is usually secured to the lower channel using a holder. A conventional nut unit securing construction is shown in FIG. 8. In this construction, a nut unit 130 is placed in a recessed nut accommodating portion 131a formed by a shock-absorbing member 131, the nut unit 130 in this state is accommodated in a space 132b of a holder 132, and an externally threaded portion 133 provided at the bottom of the holder 132 is inserted through a through hole 134a formed in a lower channel 134 and engaged with a nut 135 from the lower side of the lower channel 134. The driver shaft 136 is passed through an internally threaded hole 130a of the nut unit 130 and through holes 132a of the holder 132 concentrically arranged.
Another conventional securing construction is shown in FIG. 9. In this construction, a shock-absorbing member 141 having an opening 141b at the bottom is put on a nut unit 140 from above, a holder 142 whose middle part projects in U-shape is put on the shock-absorbing member 141, the opposite ends of the holder 142 are placed on a mount position of a lower channel 144, and bolts 145 are engaged with mount holes 142b of the holder 142 from below via mount holes 144a of the lower channel 144 to mount the nut unit 140 on the lower channel 144. An internally threaded hole 140a of the nut unit 140, through holes 141a of the shock-absorbing member 141 and through holes 142a of the holder 142 are concentrically arranged, so that a driver shaft 146 can be passed therethrough.
The movement stroke of the seat is generally restricted by mounting stoppers in the form of nuts, pins or the like on the driver shaft while spacing them apart by a suitable distance. The stopper construction is shown in FIG. 10. In this stopper construction, a transmission unit 147 is used as one stopper and a nut 148 mounted on the driver shaft 146 while being spaced apart from a transmission unit 147 is used as the other stopper. Further, there are provided resin-made washers 150 for preventing the holder 142 from colliding with the transmission unit 147 or the nut 148 to ensure strong engagement between the driver shaft 146 and the internally threaded hole 140a, thereby causing resistance when next movement is started, i.e., for preventing the so-called biting, at the colliding sides of the transmission unit 147 and the nut 148.
In recent years, it has become usual practice to mount side airbags and/or to strengthen a seat frame in order to improve the safety upon crash. This makes the weight of the seat heavier, increasing the load acting on the driver shaft and the nut unit of the power seat.
The holder 132 of the former conventional construction shown in FIG. 8 is formed by drawing, and has thus a thinned portion. Accordingly, there is the demand for such a contrivance as to prevent stresses from being concentrated on the thinned portion as the load increases.
The holder 142 of the latter conventional construction shown in FIG. 9 has a U-shaped middle part bent in a direction normal to moving directions. Thus, there is the demand for such a contrivance as to prevent the U-shaped portion from being elastically deformed.
On the other hand, the stopper construction shown in FIG. 10 has the problem of the increased number of parts since the resin-made washers 150 are separately required in addition to the transmission unit 147 and the nut 148 as the stoppers to prevent the biting.
It is an object of the present invention to provide a power seat for vehicle which is free from the problems residing in the prior art.
It is another object of the present invention to provide a power seat for vehicle which can prevent the damage of a holder and an occurrence of biting without increasing the number of parts.
According to an aspect of the invention, a power seat for a vehicle is provided with an upper channel fixedly attached to a seat, a lower channel fixedly attached to a floor of the vehicle. The lower channel is slidably engaged with the upper channel. The power seat is further provided with a nut unit fixedly attached to one of the upper channel and the lower channel, a driver shaft passing through the nut unit, a motor mounted on the other one of the upper channel and the lower channel, and a transmission unit for transmitting a torque of the motor to the driver shaft.
The nut unit includes a nut block having an internally threaded through hole through which the driver shaft passes, and a holder for holding a nut block. The holder is formed with a front standing wall, a rear standing wall, and a coupling portion coupling the front standing wall and the rear standing wall so as to define a space for holding the nut block. Each of the front standing wall and the rear standing wall has right and left buttress walls projecting outward, the ends of the right and left buttress walls that face an inner surface of the channel attached with the nut unit coming into contact with the inner surface of the channel attached with the nut unit.
These and other objects, features, and advantages of the present invention will become more apparent upon reading the following detailed description along with the accompanying drawings.